Hi AAPL,

We're told that the price of a dress was first discounted by a certain percent and again later by 25 percent of the discounted price - and that these two discounts are equivalent to a single discount of 40 percent of the original price. We're asked for the first discount. This question can be solved in a couple of different ways, including with a mix of TESTing THE ANSWERS and TESTing VALUES.

To start, since we're taking a discount OF an already discounted price, the 'base value' of the dress will be smaller for the second calculation. IF the sum of the two individual discounts was 40%, then the value of the discount would actually be LESS than that. This means that the sum of the two discounts (X + 25) will be GREATER than 40... but not much greater.

Let's TEST Answer C: 20%

IF....
The original price = $100...
a 40% discount would give us a price of $100 - (.4)($100) = $100 - $40 = $60
and
a 20% discount would give us a price of $100 - (.2)($100) = $100 - $20 = $80
followed by a 25% discount would give us... $80 - (.25)($80) = $80 - $20 = $60
The two end prices match, so this MUST be the answer.

Final Answer: C

GMAT assassins aren't born, they're made,
Rich